"What's the most powerful slingshot?" From all the questions I answered, this was by far the most common. Power seems to attract, and nobody wants to be caught with a "weak" model.
There is no such thing as the most powerful slingshot. The power is defined by the bands, not by the frame. You can attach almost any commercial band to your slingshot, and still can make more poweful bands by yourself. There only limit is your strength.
Before you start to buy speargun tubes and try turning your wristrocket into a piece of long-range artillery, be reasonable and determine how much power you need. Most usual commercial slingshots have enough power for target shooting up to 25 yards, and take quarry up to the size of a small cottontail. Do you really need more?
There are several disadvantages coming along with power. Things get more dangerous, you'll have to use more expensive ammo, your muscles will fatigue faster and, most important, your accuracy will decline. Maybe you actually can pull a slingshot with speargun tubing - but can you hold it steadily, and hit what you want? A strong bowhunter might say "of course", but most shooters can't. In my opinion, accuracy is more important tham velocity.
What most people don't know is that a there are a few little tricks to improve velocity and accuracy. Let's start with the....
Yes, the bands. I can't stress enough how important they are. They store the power, they make the pellet fly, and make you inaccurate if pull weight is too high. By exchanging them, you can completely change the slingshots' shooting characteristics.
Every shooter has his own draw length. You determine it by stretching out your arm sideways, and measuring the distance between anchor point (cheek) and the middle of the fist. As a rule of thumb, the this value should be divided by 5, and don't forget to add the lenght needed to attach the bands on the fork ends. Overly long bands are the #1 power and accuracy drain. But keep in mind that shortening the bands does decrease their lifespan, and you should do it only to a certain degree, until you feel comfortable with pull and power.
Second, align the bands properly. The pouch must be in a 90° angle to the handle, the rubber tubes must hang back relaxed, witout inner twist.
Still not satisfied? Think about getting new bands which fit better to your needs. My favourites are the Trumark bands, but Barnett, Saunders and Crosman also make good ones. The Marksman "Laserhawk" tapered bands claim to be powerful, but in fact, they are the weakest one I know. Don't hesitate to buy bands from a different brand than your slingshot is, it usually works well. Or make your own assemblies - check the rubber pages for more information!
Neat little trick: Punch a small hole right in the middle of the pouch. When you load a pellet, it is easier to center it.
You can try to punch in some additional holes for reduction of mass and friction, but be careful not to take away too much of it.
A very important issue! Steel pellets come in 1/4", 5/16", 3/8" and 1/2" size. If you use normal "heavy pull" bands, the 1/2" ball will deliver more than 4 times the energy of a 1/4" pellet! Using big ammo is absolutely essential. There is absolutely no use for a ultra-high-power band assembly, as long as you use small steel balls! Consider 3/8" as minimum if you want to make powerful shots. Every serious and ethical hunter will take 1/2". If you plan using one of these selfmade ultra-power speargun-tubing models, you have to look for big bore lead balls, or all the efforts will be worthless.
Keep it away from excessive sunlight if you don't use it. Wipe the bands with "Turtle wax 2001 Super protectant". keep it clean, and use fine sandpaper to smooth the fork ends, in case they are nicked. And don't let it rot inside an old cupboard - slingshots need a lot of love and must be shot frequently!
If you need more information, read Power and if you want some formulas, go to Science.doc